US4670885A - Spread spectrum adaptive antenna interference canceller - Google Patents
Spread spectrum adaptive antenna interference canceller Download PDFInfo
- Publication number
- US4670885A US4670885A US06/705,613 US70561385A US4670885A US 4670885 A US4670885 A US 4670885A US 70561385 A US70561385 A US 70561385A US 4670885 A US4670885 A US 4670885A
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- United States
- Prior art keywords
- signal
- spread spectrum
- signals
- responsive
- adaptive
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K3/00—Jamming of communication; Counter-measures
- H04K3/20—Countermeasures against jamming
- H04K3/22—Countermeasures against jamming including jamming detection and monitoring
- H04K3/224—Countermeasures against jamming including jamming detection and monitoring with countermeasures at transmission and/or reception of the jammed signal, e.g. stopping operation of transmitter or receiver, nulling or enhancing transmitted power in direction of or at frequency of jammer
- H04K3/228—Elimination in the received signal of jamming or of data corrupted by jamming
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
- H01Q3/2605—Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
- H01Q3/2611—Means for null steering; Adaptive interference nulling
- H01Q3/2617—Array of identical elements
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K2203/00—Jamming of communication; Countermeasures
- H04K2203/30—Jamming or countermeasure characterized by the infrastructure components
- H04K2203/32—Jamming or countermeasure characterized by the infrastructure components including a particular configuration of antennas
Definitions
- This invention relates generally to circuitry for processing spread spectrum signals and, more particularly, to circuitry for processing such signals so as to minimize interference signals received at a receiver for a spread spectrum communication system.
- Each of the antenna systems comprises a pair of properly phased quarter wavelength spaced stubs, one pair of antennas, for example, at one location and the other at a separate location.
- the outputs of each antenna system would be connected to separate receivers with the best input being selected using suitable diversity techniques.
- Such an approach seems to have limited capability, particularly where most of the potential jamming or interference signal angles of arrival are not adequately protected.
- an adaptive power equalization circuit which interfaces directly between the radio frequency (RF) antenna system and the RF or intermediate frequency (IF) port of existing spread spectrum receiver circuits.
- the adaptive power equalization circuitry is designed to sacrifice the small increment of performance associated with signal-to-interference ratios in the spread bandwidth at levels above 0 dB (i.e., where the interference signal is weaker or substantially equal to the desired communication signal), at which levels the spread spectrum gain is sufficient to permit reception of the desired transmitted signal.
- such adaptive power equalization circuitry provides interference protection over the specified dynamic range of operation of the system in addition to the spectrum spreading of the communication signal and it is in such critical region that the circuitry of the invention provides its desired improvement effects.
- circuitry in accordance with the invention maintains a signal-to-interference ratio that typically is only 2-3 dB (and at most below 5 dB) less than that of a theoretically optimum reference directed adaptive array. Accordingly, while an optimum reference directed adaptive array may yield signal-to-interference ratios better than -15 dB, the circuitry in accordance with the invention typically yields better than -18 dB to -17 dB ratios.
- a pair of antennas each receive incoming signals which may include both the desired spread spectrum communication signal and one or more undesired interference signals.
- the received signals are supplied to an adaptive power inversion circuit which produces a first, or difference, signal having a relatively low, i.e., minimized, power level and comprising primarily the weaker of the spread spectrum signals and the incoming interference signals (in effect, the larger signals are cancelled) and a second, or sum signal, which has a relatively higher power level than that of the difference signal and comprises both the spread spectrum signal and all of the incoming interference signals.
- the difference and sum signals which are so obtained through the use of the adaptive power inversion circuit are then supplied to a power equalization circuit which provides difference and sum signals which have substantially equal power levels over the intended specified dynamic range of operation of the system.
- the equalized power level signals are then combined so as to provide a spread spectrum receiver output signal which has a substantially improved signal-to-interference ratio when this ratio at the input antennas is less than 0 dB, which signal can then be supplied to a conventional spread spectrum receiver circuit.
- FIG. 1A shows in broad block diagram form a conventional spread spectrum antenna/receiver system utilizing an antenna and a spread spectrum receiver circuit
- FIG. 1B shows in broad block diagram form such an antenna/receiver system utilizing the adaptive power equalization circuitry of the invention
- FIG. 2 shows a more detailed block diagram of one embodiment of an adaptive power equalization circuit for use in FIG. 1B;
- FIG. 3 shows a performance curve which depicts the output signal-to-interference ratio as a function of input signal-to-interference ratio for a typical system in accordance with the invention
- FIG. 4 shows a block diagram of an alternative embodiment of a power equalizer/combiner circuit of FIG. 2;
- FIG. 5 shows a block diagram of an alternative embodiment of an adaptive power inversion circuit of FIG. 2;
- FIG. 6 shows an alternative arrangement of an adaptive power equalization circuitry for a spread spectrum receiver system which utilizes four antennas
- FIG. 7 shows an alternative block diagram arrangement for utilizing the invention in a different spread spectrum receiver context.
- a conventional spread spectrum receiver comprises an antenna system which utilizes, for example, a single antenna 10 the output of which is supplied to a receiver circuit 11 for processing so as to produce a received spread spectrum output signal therefrom.
- an adaptive power equalization circuit 14 is utilized as an interface between two receiver antennas 12 and 13 and receiver circuit 11 for processing the signals in such a way as to improve the signal-to-interference ratio of the signal supplied to the receiver.
- FIG. 2 A specific embodiment of the adaptive power equalization circuit of FIG. 1B is shown in FIG. 2, wherein the adaptive power equalization circuit 15 of the invention comprises a cascade of two circuits, one an adaptive power inversion circuit 15 and the other a power equalizer/combiner circuit 16.
- the function of the adaptive power inversion circuit 15 is to provide a signal at a first output port thereof, identified here as difference () port 23, which has a minimized power level obtained by effectively cancelling the strongest input signal component.
- a signal is also provided at a second output port thereof, identified here as sum () port 24, which has a much larger power level since it effectively represents the sum of all the input signal components.
- the function of the power equalizer/combiner circuit 16 is to equalize the power levels of such signals from the power inversion circuit over a specified dynamic range of operation of the system and to combine such equalizer power level signals for supply to the receiver circuit 11.
- the input from antenna 12, for example, is supplied through a preamplifier 17 to a signal splitter circuit 18 one output of which is supplied to the input of a complex multiplier 19 and the other output of of which is supplied to a complex correlator 20.
- the output of complex multiplier 19 is supplied to one input of a 180° hybrid coupler circuit 21 the other input of which is supplied from antenna 13 via preamplifier 22.
- Hybrid couple 21 produces two outputs, one identified as the output at output port 23 which output represents a difference in which the largest signal component, or components, of the input signals are cancelled, and the other identified as the output at output port 24 which output represents the sum of the input signal components.
- the difference signal is supplied to a signal splitter 25A which supplies the difference signal as a feedback signal to the other input of complex correlator 20 and as a minimized power level output from adaptive power inversion circuit 15.
- Correlator 20 provides in-phase and quadrature outputs which are supplied through low pass filters 27 to complex multiplier 19 as appropriate weighting signals.
- the in-phase and quadrature inputs of complex multipler 19 are utilized to adjust the amplitude and phase of the input signal from antenna 12 so as to suppress the strongest signal at the difference () port 23 of hybrid coupler 21.
- the signal supplied at port 24, as mentioned above, includes the sum of all the input signal components.
- the difference output at port 23 will contain the desired spread spectrum communication signal together with a relatively weak inteference signal, which has been effectively cancelled, while the sum output at port 24 will contain the relatively strong interference signal together with the spread spectrum communication signal.
- the overall power level of the difference signal at port 23 will be substantially lower (effectively minimized) than that of the sum signal at port 24.
- the difference signal is supplied from signal splitter 25A through another signal splitter 25B to one input of a power equalization control circuit 26 and to an input of combiner (summation) circuit 30.
- the sum signal at port 24 is supplied via signal splitter 28 to a voltage controlled attenuator circuit 29 and also to another input of power equalization control circuit 26.
- the output from attenuator 29 is supplied to the other input of combiner circuit 30.
- Control circuit 26 is arranged as would be known to those in the art to provide a control signal as a function of the power level difference between the ⁇ and ⁇ signal inputs thereto which controls the voltage at the voltage controlled attenuator so as to control the attenuation of the sum signal from signal splitter 28 so that at the inputs to combiner circuit 30 the power level of the signal from signal splitter 25B and the power level of the signal from the output signal of attenuator circuit 29 are substantially equal over a specified dynamic range of operation of the system.
- Such equalized power level signals are then combined in circuit 30 to provide an output receiver signal for use by receiver circuit 11.
- the summed signal supplied to receiver 11 will contain substantially equal proportions of the interference signals and the desired spread spectrum communication signal.
- the spread spectrum gain of the signal in receiver 11 will then be sufficient to permit demodulation thereof to provide the desired receiver output signal for use by the communication system of which the receiver circuit is a part.
- the signal-to-interference ratio will be substantially improved over the system dynamic operating range utilizing the adaptive power equalization circuitry of the invention and the larger the interference signal the larger the improvement which will occur.
- the circuitry of the invention can be used in the presence of weak interference and even in the absencee of any interference at all.
- the overall signal-to-noise ratio can be reduced when a desired spread spectrum communication signal is present but little or no interference is present.
- the difference signal will primarily comprise "noise" or weak interference signals (the desired relatively stronger spread spectrum signal being effectively cancelled) and the sum signal will primarily comprise the stronger spread spectrum signal plus the weak interference and noise signal.
- Equalization of the power levels thereof will still permit the receiver to demodulate the desired signal for use by the system due to its sufficient spread spectrum gain characteristics.
- noise alone no real interference signal
- the above operation will also occur and the signal-to-noise ratio will be reduced to 0 dB over the full band. Accordingly, since receiver spread spectrum gain allows operation well below a 0 dB signal-to-interference ratio, there is virtually no penalty due to the insertion of the adaptive power equalization circuitry in the receiver system even under conditions where substantially little or no interference is present.
- FIG. 3 shows a graph which depicts exemplary curves of output signal-to-interference ratios as a function of the input signal-to-interference ratios obtainable when using the adaptive power equalization techniques of the invention.
- the power equalizer circuit of the embodiment shown in FIG. 2 is useful for providing effective operation over a specified dynamic range of operation. For example, it is generally effective where the range of input signal-to-interference ratios up to -30 dB, it may be found that in some applications where the desired signal power is much weaker in comparison with the interference signal power, attenuations much greater than that tend to provide signals of equalized power levels which are sufficiently low as to be in the order of magnitude of noise signals which may be present. To extend the operating range, an alternative embodiment of such power equalization operation can be achieved using an embodiment depicted in FIG. 4, for example.
- both the ⁇ -output and the ⁇ -output from power inversion circuit 15 can be supplied to automatic gain control (AGC) circuits 31 and 32, respectively, each arranged to provide automatic gain operation, using well-known AGC circuitry techniques, set in each to provide the same desired power level outputs therefrom so that equalized power level signals from AGC circuits 31 and 32 are supplied to combiner circuit 33.
- AGC automatic gain control
- the gain controls in each case can be arranged to provide equalized power levels over a wide dynamic range of operation, as desired.
- FIG. 5 A further alternative embodiment of the circuitry of FIG. 2 is shown in FIG. 5 with respect to the adaptive power inversion circuit thereof.
- the circuit of FIG. 5 makes use of delay circuitry and added complex weighting circuits.
- the input signals from antenna 12 and preamplifier 17 is supplied to a signal splitter 34 and thence to signal splitter 18 for use as in FIG. 2 for providing an adjustment of the amplitude and phase by the weights generated by the complex correlator 20, filters 27, and multiplexer 19, as before.
- the weighted output is supplied to signal combiner 35 where it is combined with the weighted output from a complex multipler 36 for providing an input signal to hybrid coupler 21.
- the complex multiplier 36 in conjunction with complex correlator 38 and low pass filters 37 produce a weighted output of the input signal delayed by a controlled time delay at delay circuit 40 which receives the input signal from signal splitter 34 and supplies a delayed input signal to signal splitter 39 for use by complex correlator 38 and complex multipler 36.
- the feedback inputs to correlators 20 and 38 are supplied from the output of hybrid coupler 21 via signal splitters 25A and 41, as shown.
- the non-delayed and delayed input signals can be achieved by utilizing, for example, a conventional tapped delay line for such purpose.
- the use of such delayed signal technique using more than one adaptive power inversion loop tends to improve the suppression of wideband noise-like interference over that achievable with a single adaptive loop of FIG. 2.
- the circuit of FIG. 5 can be further extended by using a greater number of adaptive loops operating with a number of different delays of the input signal. Such operation can be achieved by using a multiple tapped delay line for such purpose.
- the circuitry can also be extended to the use of more than two antennas, thus allowing it to suppress more effectively multiple interference signals.
- Such a system is depicted in FIG. 6 for use with four antennas.
- the overall adaptive power equalization circuitry comprises multiple adaptive power inversion circuits and a single power equalizer/combiner circuit.
- a pair of input antennas 42 and 43 supply input received signals at the inputs of adaptive power inversion circuit 44 which is of the same type as those discussed above in FIGS. 2 and 5, for example.
- a second pair of antennas 45 and 46 supply input received signals to a similar adaptive power inversion circuit 47.
- the difference signal outputs from circuits 44 and 47 are supplied to the inputs of a further adaptive power inversion circuit 48, while the sum signal outputs from circuits 44 and 47 are supplied to the inputs of a still further adaptive power inversion circuit 49.
- the difference output from adaptive power inversion circuit 49 is supplied to one input of a further adaptive power inversion circuit 50, while the sum output of inversion circuit 48 is supplied to the other input thereof.
- the difference output from inversion circuit 48 is supplied to one input of adaptive power inversion circuit 51, the other input of which is obtained from the difference output port of inversion circuit 50 as shown.
- the ( ⁇ ) output from inversion circuit 51 will have the three strongest signal components cancelled.
- the ( ⁇ ) output from inversion circuit 51 will have only the two strongest signal components cancelled.
- the ( ⁇ ) output from inversion circuit 50 will have only the strongest signal component cancelled.
- the ( ⁇ ) output from the inversion circuit 49 will contain all the signal components. For example, with only the desired signal present, only the ( ⁇ ) port from circuit 42 will contain that signal, the other will contain only noise.
- the difference output of inversion circuit 51, the sum output therefrom, the sum output from inversion circuit 50 and the sum output from inversion circuit 49 are all supplied to an appropriate power equalizer/combiner circuit 52 which is arranged to equalize the power levels in each of its four input signals, as by using appropriate AGC circuitry techniques, for example, as discussed above. These equalized power level signals are then combined to produce the output receiver signal for supply to receiver 11.
- the signal-to-interference ratio of the output signal will tend to be closer to -5 dB rather than to the 0 dB obtained for a two antenna system.
- the system can be extended to an N-antenna system, utilizing the approach depicted, in the general case the output signal-to-interference ratio being expressed as -10 log 10 (N-1).
- the four antenna system shown in FIG. 6 achieves such output signal-to-interference ratio with up to three different interference waveforms.
- an N-antenna system can handle up to N-1 interference waveforms, the general case requiring a specified number of adaptive power inversion circuits which can be expressed as N(N-1)/2.
- Still another embodiment of a four antenna system which utilizes a pair of receivers and, in effect, provides for diversity type operation in which a selection of the best receiver output is obtained using conventional diversity selection techniques as depicted in FIG. 7.
- a first pair of antennas 53 and 54 are used to supply input signals to an adaptive power equalization circuit 55 in accordance with the invention while a second pair of antennas 56 and 57 are used to supply inputs to a second adaptive power equalization circuit 58 in accordance with the invention.
- the outputs of circuits 55 and 58 are supplied, respectively, to separate receivers 59 and 60 which provide signals which can be appropriately selected utilizing diversity receiver selection circuity 61.
- the latter circuitry is well knwon to those in the art for selecting a signal from one of two or more which has the greater signal-to-interference ratio for use as an output signal therefrom for supply to the rest of the communication system.
- the antenna pairs utilized therein can be placed, for example, at different locations for looking in different directions so as to take care of interference problems that are expected to be received from such different directions.
- the system of FIG. 7 can be extended to N-antennas and N/2 diversity channels.
- Adaptive power equalization circuitry in accordance with the invention can be designed for use either at RF frequencies or at IF frequencies and can be positioned so as to interface either the RF or IF portions of a receiver system. While the invention has been described above in various embodiments, other modifications thereof utilizing the inventive concept described may be devised by those in the art within the spirit and scope of the invention. Hence the invention is not to be limited to the particular embodiments described above, except as defined by the appended claims.
Abstract
Description
Claims (16)
Priority Applications (7)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/705,613 US4670885A (en) | 1985-02-26 | 1985-02-26 | Spread spectrum adaptive antenna interference canceller |
IL77861A IL77861A (en) | 1985-02-26 | 1986-02-11 | Spread spectrum adaptive antenna interference canceller |
CA000502190A CA1250911A (en) | 1985-02-26 | 1986-02-19 | Spread spectrum adaptive antenna interference canceller |
DE8686902592T DE3675858D1 (en) | 1985-02-26 | 1986-02-24 | INTERFERENCE COMPENSATOR FOR ADAPTIVE ANTENNA WITH BAND SPREAD RECEIVER. |
JP61502260A JPS62500418A (en) | 1985-02-26 | 1986-02-24 | Dispersed Spectrum Compatible Antenna Communication Jammer Canceller |
EP86902592A EP0215117B1 (en) | 1985-02-26 | 1986-02-24 | Spread spectrum adaptive antenna interference canceller |
PCT/US1986/000393 WO1986005050A1 (en) | 1985-02-26 | 1986-02-24 | Spread spectrum adaptive antenna interference canceller |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/705,613 US4670885A (en) | 1985-02-26 | 1985-02-26 | Spread spectrum adaptive antenna interference canceller |
Publications (1)
Publication Number | Publication Date |
---|---|
US4670885A true US4670885A (en) | 1987-06-02 |
Family
ID=24834228
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US06/705,613 Expired - Lifetime US4670885A (en) | 1985-02-26 | 1985-02-26 | Spread spectrum adaptive antenna interference canceller |
Country Status (7)
Country | Link |
---|---|
US (1) | US4670885A (en) |
EP (1) | EP0215117B1 (en) |
JP (1) | JPS62500418A (en) |
CA (1) | CA1250911A (en) |
DE (1) | DE3675858D1 (en) |
IL (1) | IL77861A (en) |
WO (1) | WO1986005050A1 (en) |
Cited By (49)
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US5103460A (en) * | 1989-10-17 | 1992-04-07 | Clarence H. Stewart | Spread spectrum intercept apparatus and method |
US5113409A (en) * | 1989-10-17 | 1992-05-12 | Stewart Clarence H | Spread spectrum intercept apparatus and method |
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US5369663A (en) * | 1991-03-05 | 1994-11-29 | The United States Of America As Represented By The Secretary Of The Navy | Spatial combiner for a digital VLF/LF receiver |
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US20080076360A1 (en) * | 2006-09-22 | 2008-03-27 | Northrop Grumman Corporation | Apparatus for combining two radios on a single antenna |
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US20110080923A1 (en) * | 2002-09-20 | 2011-04-07 | Rambus Inc. | Interference Suppression for CDMA Systems |
US8005128B1 (en) | 2003-09-23 | 2011-08-23 | Rambus Inc. | Methods for estimation and interference cancellation for signal processing |
US8085889B1 (en) | 2005-04-11 | 2011-12-27 | Rambus Inc. | Methods for managing alignment and latency in interference cancellation |
US8654689B2 (en) | 2002-09-20 | 2014-02-18 | Rambus Inc. | Advanced signal processors for interference cancellation in baseband receivers |
US9172456B2 (en) | 2005-04-07 | 2015-10-27 | Iii Holdings 1, Llc | Iterative interference suppressor for wireless multiple-access systems with multiple receive antennas |
CN115589235A (en) * | 2022-11-29 | 2023-01-10 | 湖北中环测计量检测有限公司 | Indoor environment detection data interaction method of multiplex communication model |
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- 1986-02-24 EP EP86902592A patent/EP0215117B1/en not_active Expired - Lifetime
- 1986-02-24 WO PCT/US1986/000393 patent/WO1986005050A1/en active IP Right Grant
- 1986-02-24 DE DE8686902592T patent/DE3675858D1/en not_active Expired - Fee Related
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Also Published As
Publication number | Publication date |
---|---|
EP0215117A4 (en) | 1987-07-22 |
CA1250911A (en) | 1989-03-07 |
IL77861A (en) | 1989-10-31 |
JPS62500418A (en) | 1987-02-19 |
DE3675858D1 (en) | 1991-01-10 |
EP0215117B1 (en) | 1990-11-28 |
EP0215117A1 (en) | 1987-03-25 |
WO1986005050A1 (en) | 1986-08-28 |
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